1. Field of the Invention
The present invention generally relates to process control systems, and more specifically to a method and apparatus for managing field devices having different device description specifications in a process control system.
2. Related Art
A process control system generally contains several field devices, which are operable to implement a desired control process (e.g., oil refinery, manufacturing operation, etc.). Examples of field devices include valves, positioners and switches, which are controlled to implement the control process.
Field devices may provide status related to the operation of the field device. For example, the status information could indicate temperature, pressure, extent of opening of a valve, light intensity, whether the device is malfunctioning (e.g., output saturated, input open), configuration values, calibration status, etc., of the field devices.
There is a general need to manage field devices provided in a process control system. Management generally refers to tasks such as monitoring and configuration of the devices. Monitoring generally entails retrieving and displaying of the status information such as that noted above. On the other hand configuration generally entails writing data into a variable of the field device.
To facilitate such management of field devices, a device description (DD) is often provided by a vendor associated with a field device.
The device description defines the manner in which commands for a corresponding field device can be issued and the manner in which the response (resulting from issuing of the management commands) is to be interpreted. The DD also contains the information about how the data should be organized and presented to the user.
The definitions in DDs are generally provided according to a DD (language) specification, which specifies the syntax (grammar) and semantics (meaning) for the definitions. Examples of DD (or DDL) specifications include HART DDL Specification 500, FF DDL specification, Profibus DDL specification etc., which are all well known in the relevant arts.
In general, using a DD specification, device description corresponding to various device types can be specified. The device description is often provided in a file, which is generally referred to as a DD file.
A typical task associated with the management of a field device is to read and decode (parsing) a corresponding DD file for extracting the desired information. Due to the differences in aspects such as syntax and semantics of various DD specifications, a prior embodiment implements multiple parsing blocks, with each parsing block being implemented to read and decode a device description file in the corresponding specification.
Due to such multiple parsing blocks, integration of new set of field devices having device description information according to a new DD specification may present additional challenges (implementation overhead and cost). In addition, the corresponding implementations may require additional memory and processing power during operation/run-time, which could be problematic particularly in the case of thin clients.
Accordingly, what is needed is a method and apparatus which overcomes at least some of such disadvantages while managing field devices having different device description specifications in a process control system.